This invention relates to an article, system and method used for creating solid immersion lens array with marks.
Recent advances in optics provide for a method of image capture on a length scale much smaller than previously realized. Such near-field optical methods are realized by placing an aperture or a lens in close proximity to the surface of the sample to be imaged. Others (see, for example, the review by Q. Wu, L. Ghislain, and V. B. Elings, Proc. IEEE (2000), 88(9), pg. 1491-1498) have developed means of exposure by the use of the solid immersion lens (SIL). Special methods for positioning control of the aperture or lens are required, as the distance between the optical elements (aperture or lens) and the sample is extremely small. The SIL can be positioned within approximately 0.5 micrometer of the target surface by the use of special nano-positioning technology. SIL technology offers the advantage that the lens provides a true image capture capability. For example, features in a real object can be faithfully captured in an image of reduced spatial extent. In the case of the SIL, images can be captured much smaller than the image size achievable through the use of conventional or classical optics. Such conventional optics are said to be diffraction-limited because the size of the smallest feature in an image is limited by the physical diffraction.
If a SIL is placed in contact with the sample under examination, illumination can be more readily focused on it, and use of the high NA of the system allows efficient collection of the excitation light with high optical transmission efficiency and observation of the sample with very high resolution. Methods for molding a single solid immersion lens as part of a are disclosed in U.S. Pat. No. 6,301,055. Illumination of a limited field of view within a single flow channel of a sample material is described.
The problem is that a single solid immersion lens mounted on a microscope or attached as an integral part of a limits the area of view of the sample to a single location, the area directly beneath the solid immersion lens. A method for molding a multiplicity of solid immersion lenses as part of a cover slide is described in U.S. patent application Ser. No. 10/171,168 entitled xe2x80x9cSolid Immersion Lens Array And Methods For Producing Solid Immersion Lens Arrayxe2x80x9d by David L. Patton et al., filed concurrently herewith.
In near-field microscopy, the solid immersion lens is used in a microscope in conjunction with other optical elements such as the microscope objective. To avoid large losses in a multi-lens system, the alignment of each lens and optical article with subsequent lenses and optical articles must be very precise. Fiducial marks are often created on the lenses and optical articles outside the optical ray path to serve as a reference point during alignment. Fiducial marks are particularly important in the case of aspheric lenses and lens arrays where it is difficult to identify the center of the lens during alignment activities. As optical systems get smaller for fiber optics applications, like telecommunications and optical sensors, the need increases for precise alignment of the optical components and the accuracy of the associated fiducial marks. Alignment specifications of two (2) microns are now common with a desire to deliver sub-micron alignment accuracy. Consequently, the fiducial marks must be located with an accuracy of one micron or better.
Fiducial marks are well known in the semi-conductor manufacturing industry as an important tool for making multi-layer semiconductors. In this case, the fiducial marks are incorporated as part of the semiconductor circuit plan. Due to the thinness (50-100 micron) of the semiconductor layers used in making multi-layer semiconductors, the fiducial marks of multiple semiconductor layers can be viewed simultaneously in separate layers using a high magnification microscope. The high magnification microscope aids in positioning the fiducial marks of one semiconductor layer over the fiducial marks of another semiconductor layer during the alignment process. Forming fiducial marks in optical articles raises special challenges in that optical surfaces are typically relatively thick; often well over 1000 microns in thickness. This is the case even in a micro lens array that has micro lenses that are well under a millimeter in diameter. The thickness of the micro lens array makes it virtually impossible to accurately locate a fiducial mark by looking through the micro lens array due to optical limitations. On the one hand, the location accuracy of the fiducial mark relative to the optical article is limited because the fiducial mark is displaced by refracted light passing through the micro lens array material. Moreover, the thickness of the micro lens array limits how close the microscope used for identifying the micro lens array can be positioned to the fiducial mark. Consequently, only lower magnification microscope objectives or more expensive long working distance objectives, can be used to look at the fiducial. Therefore, for optical articles, a method of applying a very accurately located fiducial mark on the side opposite to the optical article is needed.
In U.S. Pat. No. 6,005,294, by Tsuji et al., Dec. 21, 1999, entitled xe2x80x9cMethod Of Arranging Alignment Marks,xe2x80x9d a method of making semiconductor devices uses multiple fiducial marks in such a way that the area occupied by the fiducial marks is reduced and the manufacturing productivity is correspondingly increased. While this patent does describe the state of the art for making semiconductor devices, the alignment process described therein is not appropriate for optical articles like lens arrays. As mentioned, in lens arrays, the significant thickness of the various lenses makes it impossible to view fiducial marks from multiple optical articles simultaneously due to the separation distance imparted by the material thickness of the lenses.
Also, U.S. Pat. No. 5,850,276, by Ochi et al., Dec. 15, 1998, entitled xe2x80x9cMethod Of Making LCD Device Having Alignment Mark Made Of Same Material And Formed At Same Time As Micro lensesxe2x80x9d and U.S. Pat. No. 5,771,085, by Ochi et al., Jun. 23, 1998, entitled xe2x80x9cLCD Device With an Alignment Mark Having Same Material As Micro lensesxe2x80x9d each describe a process for molding fiducial marks into a micro lens screen used for liquid crystal display devices. In these patents the shapes of the fiducial marks are also described in detail. The fiducial marks as described are protrusions in the shape of a cross or several other variations, located on the same side as the micro lenses. The protrusions can be semicircular in cross section or another shape as long as the grooves between the protrusions stand out as dark lines when viewed with a reflecting microscope. The references recognize that lens characteristics, such as thickness, interfere with the ability to identify underlying fiducial marks. Further, the references show some appreciation for useful geometries of fiducial marks and for fiducial marks molded along with a micro lens array. However, neither of the patents show appreciation for fiducial marks applied on the side opposite the optical surfaces in the micro lens array. Furthermore, there is no appreciation by either of the references that advantages can be gained with a molded fiducial mark having lens characteristics.
Moreover, U.S. Pat. No. 6,096,155, by Harden et al., Aug. 1, 2000, entitled xe2x80x9cMethod Of Dicing Wafer Level Integrated Multiple Optical Elementsxe2x80x9d discloses the use of fiducials to aid in alignment of micro lenses on wafers during the bonding of multiple wafers together prior to dicing. This patent generally teaches making integrated multiple optical elements with features to help control the thickness of adhesives and solders used to bond together the wafers. While effective use of the fiducial marks is described, there is absolutely no mention of ways to improve alignment of fiducial marks on one side with the optical element on the other side of the wafer. The techniques of embossing and molding fiducial marks, described in the patent, both suffer from locational inaccuracies from one side to the other of the order of plus or minus ten (10) microns. In molded micro lenses and micro lens arrays this inaccuracy is not acceptable.
Furthermore, U.S. Pat. No. 4,598,039, by Fischer et al., Jul. 1, 1986, entitled xe2x80x9cFormation Of Features In Optical Materialxe2x80x9d describes the use of a laser to remove optical material in a controlled fashion. The laser can be used directly on the optical material or a layer of ablative absorber material can be put onto the surface of the optical material to enhance the coupling to the laser. This ablative technique is well suited to making fiducial type marks for alignment. However, the reference does not show appreciation for how to align the laser with a lens array that is located on the opposite side from the desired location for the fiducial marks.
Furthermore, U.S. Pat. No. 6,594,084 B1 xe2x80x9cMethod for Manufacturing a Precisely Aligned Microlens Arrayxe2x80x9d to Border et al.; U.S. patent application Publication No. 2003/0117482 A1 xe2x80x9cMethod of Forming Fiducial Marks on a Micro-Sized Articlexe2x80x9d to Border et al.; U.S. Pat. No. 6,515,800 B1 xe2x80x9cMicrolens Arrayxe2x80x9d to Border et al.; U.S. Pat. No. 6,587,274 B1 xe2x80x9cDouble-Sided Microlens Array and Method of Manufacturing Samexe2x80x9d to Border et al.; U.S. patent application Publication No. 2003/0118071 A1 xe2x80x9cLaser Array and Method of Making Samexe2x80x9d to Border et al.; and U.S. patent application Publication No. 2003/0118290 A1 Fiber xe2x80x9cOptic Array and Method of Making Samexe2x80x9d to Border et al. all describe the use of an optical element in conjunction with a high intensity beam to create a fiducial mark on the opposite surface to the optical feature(s) of interest.
Automatic scanning of microscope slides in a prescribed pattern, including the use of a reference mark for enabling automatic monitoring of the position of the slide is known and described in U.S. Pat. No. 4,833,382 xe2x80x9cMethod and Apparatus for use in microscope investigationsxe2x80x9d by Gibbs, May 23, 1989. Furthermore, U.S. Pat. No. 6,175,642 B1, xe2x80x9cDevice for Automatically Positioning and Centering a Microscope Optical Headxe2x80x9d by Gobbi et al. Jan. 16, 2001, describes the use of image analysis to process the image obtained by the microscope to identify specific shapes and orientations of light distributions within said image.
It is an object of the present invention to provide means to create fiducial marks on an optical element consisting of an array of solid immersion lenses in order to facilitate the proper location of the solid immersion lens relative to the optic axis of a system and to enable auto-position scanning of a microscope incorporating such a solid immersion lens array.
In accordance with one aspect of the present invention there is provided a method for positioning, in a repeatable manner, a near-field optic lens array, comprising the steps of
providing a cover slide having a near field solid immersion lenses array having least one fiducial mark;
placing the cover slide in a positioning device;
locating the at least one fiducial mark by the positioning device; and
locating the center of each lens in the array with respect to the at least one fiducial mark.
In accordance with another aspect of the present invention there is provided a solid immersion lens array comprising:
a plurality of solid immersion lenses;
a body portion in which the plurality of solid lenses are integrally secured, the body portion having a surface designed to engage a sample for viewing of the sample through the plurality of solid immersion lenses; and at least one fiducial mark located on the body portion that can be used to locate the location of each lens of the plurality of solid immersion lens.
In accordance with yet another aspect of the present invention there is provided a system for viewing individual lens provided in a solid immersion lens array comprising:
a solid immersion assembly having a body portion in which a plurality of solid lenses are integrally secured, the body portion having a surface designed to engage a sample for viewing of the sample through the plurality of solid immersion lenses, and at least one fiducial mark located on the body portion that can be used to locate the location of each lens of the plurality of solid immersion lens;
a viewing device for individually viewing each lens; and
a positioning device on which the body portion is placed and moving the body with respect to the viewing device, the positioning device using at least one fiducial mark for locating and positioning each lens with respect to the viewing device.
In accordance with still another aspect of the present invention there is provided a method for making near-field optic lens array wherein each lens of the lens array can be viewed and located individually, comprising the steps of
providing a cover slide having a near field solid optical lens array having at least one fiducial mark;
providing at least one fiducial mark on the cover slide; and
providing a unique identifier on the cover slide that can be used to retrieve locating information for each lens with respect to the at least one fiducial mark.
In accordance with another method according to the present invention there is provided a method for making near-field optic lens array wherein each lens of the lens array can be viewed and located individually, comprising the steps of
providing a cover slide having a near field solid optical lens array having at least one fiducial mark;
providing at least one fiducial mark on the cover slide;
determining the location of each of the lenses of lens array with respect to the at least one fiducial mark;
providing a unique identifier on the cover slide; and
storing the locating information in association with the unique identifier such that the unique identifier can be used to retrieve the locating information with respect to the at least one fiducial mark.